In a large mixing bowl, combine dark brown sugar, finely ground white pepper, rice flour, salt, grated garlic, soy sauce, vinegar, and unsweetened pineapple juice. Stir vigorously until smooth.

Add the skinless chicken thigh fillets to the marinade, ensuring they are coated and submerged. Cover or transfer to a resealable bag and refrigerate for at least 1 hour, preferably overnight.

In a skillet, transfer marinated chicken and any excess marinade with 1 cup of water. Heat until boiling, then reduce heat to low and simmer uncovered for 15-20 minutes.

Once liquid thickens, drizzle cooking oil over chicken and increase heat to medium. Fry the chicken pieces until they develop a charred glaze, about 5-10 minutes.

Transfer Chicken Tocino onto a serving dish and serve with garlic fried rice and spiced vinegar.